1. Field of the Invention
The present invention relates to improvement in a hydraulic joint structure used in a hydraulically-actuated device.
2. Description of Related Art
Rebar cutters and rebar benders have been conventionally known as a portable hydraulic tool (hydraulically-actuated device). Such a hydraulic tool includes, for example, a battery-driven hydraulic pump unit (hydraulic pressure generating unit) and an end tool unit (head unit) such as a cutter unit or a bending unit that is driven by a pressurized hydraulic oil supplied from the hydraulic pump unit. Recently, such a hydraulic tool is used also as a rescue tool. In order to allow the hydraulic pump unit to be shared by various end tool units, the hydraulic pump unit and the end tool unit can be connected and separated to and from each other. In addition, in order to reduce the weight load on an operator who accesses a work object, the hydraulic pump unit and the end tool unit are connected through a relatively long hydraulic hose unit. In this case, a main operator holds and operates the end tool unit, and a sub operator holds and operates the hydraulic pump unit.
The aforementioned portable hydraulic tool is classified into a single-acting type (in which only the forward action is performed hydraulically, while the backward action is performed by a return spring) and a double-acting type (in which both the forward and backward actions are performed hydraulically). In a double-acting portable hydraulic tool, two hydraulic oil lines are provided between the hydraulic pump unit and the end tool unit. One of the hydraulic oil lines is used for feeding pressurized hydraulic oil to the end tool unit, and the other is used for return oil. In a case that the portable hydraulic tool is composed of a plurality of connectable/separable units as described above, the hydraulic oil lines (oil passages) must be connected/separated. To this end, couplers or joints for constituting a hydraulic joint structure are provided on the respective units.
An example of a hydraulic joint structure for a double-acting hydraulic tool, which includes a plurality of connectable/separable units, is disclosed in Patent Document 1 (Publication of Examined Patent Application No. JPH05-037796B2), Patent Document 1 describes that two holes into which both a porting connector and a coupler can be inserted are provided in an end surface of each unit, and two hydraulic oil lines are connected by using two porting connectors, with the end surfaces of the two units being abutted with each other; or a male coupler and a female coupler are engaged with the holes by screw fastening, and the couplers are connected with each other when two units are joined.
In the system disclosed in Patent Document 1, either when a porting connector is used or when a coupler is used, two pairs of members must be positioned accurately at the same time, which complicates the joining operation. When a porting connector is used, hydraulic oil in oil passages leaks outside upon separation of the units. When a coupler is used, the leakage problem can be avoided. However, if a pump unit is operated by mistake when the two units are separated, pressurized hydraulic oil may spout, or the pump unit may be damaged.